1. Field of the Invention
The invention relates to dual port random access memory storage cells which are accessible from two different address ports.
2. Brief Description Of The Prior Art
Briefly described, random access memory cells of many varieties are well known in the art. However, such prior art cells are ordinarily addressable only from a single port. In other words, a binary address addressing a particular RAM cell causes a single select line or a coincidence of two select lines, such as a row select line and a column select line, to cause the addressed cell to be selected. Data is then sensed from or written into the selected storage cell on one or two bit sense lines. In many RAM cells, a single selection line causes the particular cell to be selected, and other selection circuitry activated by the same address causes the bit-sense lines to be selected. However, there are never any options for addressing and sensing and writing. The same selection lines and the same bit sense lines are always utilized to access and write and sense a particular location. A particular location is always represented by a single storage element. Master slave flip-flops are well known, but these are not accessible and addressable from two separate ports, and they are not bidirectional. Consequently, the storage devices of the prior art cannot be simultaneously addressed and accessed from separate sources. In certain applications especially those involving an arithmetic logic unit, this is a disadvantage.